hardware design v1 00 2

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Figure 10: Powered on/down module using button
The power on scenarios is illustrated as following figure.
Figure 11: Timing of power on module
When power on procedure is completed, SIM900R will send following URC to indicate that the module is ready
to operate at fixed baud rate.
RDY
This URC does not appear when autobauding function is active.
Note: User can use AT command “AT+IPR=x” to set a fixed baud rate and save the configuration to non-volatile flash memory.
After the configuration is saved as fixed baud rate, the Code “RDY” should be received from the serial port every time when
SIM900R is powered on. For details, please refer to the chapter “AT+IPR” in document [1].
4.2.2 Power down SIM900R
SIM900R will be powered down in the following situations：
z Normal power down procedure: power down SIM900R by the PWRKEY pin.
z Normal power down procedure: power down SIM900R by AT command “AT+CPOWD=1”.
z Abnormal power down: over-voltage or under-voltage automatic power down.
z Abnormal power down: over-temperature or under-temperature automatic power down.
4.2.2.1 Power down SIM900R by the PWRKEY Pin
User can power down SIM900R by pulling down the PWRKEY pin for at least 1 second and release. Please refer
to the power on circuit. The power down scenario is illustrated in following figure.
SIM900R_Hardware Design_V1.00 18 2012-07-20